Method and device for performing measurement based on discovery signals

ABSTRACT

One disclosure of the present specification provides a method for performing measurement based on discovery signals. The method may comprise the steps of: receiving, from cells, discovery signals based on cell-specific reference signals (CRSs); and performing measurement based on the CRS-based discovery signals for a predetermined measurement period. If a measurement bandwidth is six resource blocks (RBs), the predetermined measurement period can be determined by 5*the measurement occasion periodicity of the discovery signals. If the measurement bandwidth is 25 resource blocks (RBs), the predetermined measurement period can be determined by 3*the measurement occasion periodicity of the discovery signals. Also, the discovery signals can be received for a discovery signal occasion duration defined by N consecutive subframes.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to mobile communication.

Related Art

3rd generation partnership project (3GPP) long term evolution (LTE)evolved from a universal mobile telecommunications system (UMTS) isintroduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequencydivision multiple access (OFDMA) in a downlink, and uses singlecarrier-frequency division multiple access (SC-FDMA) in an uplink. The3GPP LTE employs multiple input multiple output (MIMO) having up to fourantennas. In recent years, there is an ongoing discussion on 3GPPLTE-advanced (LTE-A) evolved from the 3GPP LTE.

As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 10)”, a physical channel of LTE may be classified into adownlink channel, i.e., a PDSCH (Physical Downlink Shared Channel) and aPDCCH (Physical Downlink Control Channel), and an uplink channel, i.e.,a PUSCH (Physical Uplink Shared Channel) and a PUCCH (Physical UplinkControl Channel).

Meanwhile, in a next-generation mobile communication system, it isexpected that a small cell having a small cell coverage radius is addedwithin a coverage of a macro cell.

However, if small cells are densely distributed within the coverage of amacro cell, it may be difficult for a UE to quickly detect the smallcells.

To solve the problem above, a small cell may transmit a new discoverysignal (DS) in addition to existing PSS/SSS.

Meanwhile, it has not been studied yet as to the total number ofmeasurement required to achieve desired measurement accuracy when the UEattempts to perform measurement based on the discovery signal.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to solve theabove-mentioned problems.

To achieve the foregoing aspect, there is provided a method forperforming measurements based on a discovery signal. The method maycomprise: receiving, from a cell, a cell-specific reference signal (CRS)based discovery signal; and performing measurements based on the CRSbased discovery signal during a predetermined measurement period. Here,if a measurement bandwidth corresponds to 6 resource blocks (RBs), thepredetermined measurement period is determined to be equal to 5*anoccasion periodicity for measuring the discovery signal. And, if themeasurement bandwidth corresponds to 6 RBs, the predeterminedmeasurement period may be determined to be equal to 3*the occasionperiodicity for measuring the discovery signal. Also, the discoverysignal may be received during an occasion duration defined as Nconsecutive subframes.

The occasion periodicity for measuring the discovery signal maycorrespond to one of 40 ms, 80 ms, and 160 ms.

A value of the N may be equal to or more than one.

In the performing of the measurement, a discontinuous reception (DRX)may not be used.

The discovery signal may include one or more of a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),a cell-specific reference Signal (CRS) and a channel state informationreference signal (CSI-RS).

To achieve the foregoing aspect, there is provided a terminal forperforming measurements based on a discovery signal. The terminal maycomprise: a radio frequency (RF) unit configured to receive, from acell, a cell-specific reference signal (CRS) based discovery signal; anda processor configured to perform measurements based on the CRS baseddiscovery signal during a predetermined measurement period. Here, if ameasurement bandwidth corresponds to 6 resource blocks (RBs), thepredetermined measurement period is determined to be equal to 5*anoccasion periodicity for measuring the discovery signal. And, if themeasurement bandwidth corresponds to 6 RBs, the predeterminedmeasurement period may be determined to be equal to 3*the occasionperiodicity for measuring the discovery signal. Also, the discoverysignal may be received during an occasion duration defined as Nconsecutive subframes.

According to the disclosure of the present invention, the problem of theconventional technology described above may be solved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a wireless communication system.

FIG. 2 illustrates a structure of a radio frame according to FDD in 3GPPLTE.

FIG. 3 illustrates a structure of a downlink radio frame according toTDD in the 3GPP LTE.

FIG. 4 is an exemplary diagram illustrating a resource grid for oneuplink or downlink slot in the 3GPP LTE.

FIG. 5 illustrates a structure of a downlink subframe.

FIG. 6 illustrates the architecture of an uplink sub-frame in 3GPP LTE.

FIG. 7 illustrates a frame structure for the transmission of asynchronization signal in an FDD frame.

FIG. 8 illustrates an example of a frame structure for sending asynchronization signal in a TDD frame.

FIG. 9 illustrates one example of a pattern according to which a CRS ismapped to an RB in case a base station uses one antenna port.

FIG. 10 illustrates measurement and a measurement report procedure.

FIG. 11 illustrates one example of an RB to which a CSI-RS is mappedamong reference signals.

FIG. 12 illustrates a heterogeneous network in which a macro cell andsmall cells are mixed, which may evolve to the next-generationcommunication system.

FIG. 13 illustrates a situation in which small cells are distributeddensely.

FIG. 14 illustrates an example in which small cells transmit a discoverysignal.

FIG. 15 illustrates a discovery signal.

FIG. 16 illustrates a measurement process based on a discovery signal.

FIGS. 17a to 17c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 6 RBs.

FIGS. 18a to 18c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 25 RBs.

FIGS. 19a to 19c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 50 RBs.

FIGS. 20a to 20c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 6 RBs.

FIGS. 21a to 21c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 25 RBs.

FIGS. 22a to 22c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 50 RBs.

FIGS. 23a to 23c illustrate Pd with respect to acquisition time(AcqTime) when Es/Noc=−0.75 dB, and propagation condition corresponds toAGWN, EPA5, and ETU30 respectively.

FIG. 24 illustrates a block diagram of a wireless communication systemin which the present invention is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, based on 3rd Generation Partnership Project (3GPP) longterm evolution (LTE) or 3GPP LTE-advanced (LTE-A), the present inventionwill be applied. This is just an example, and the present invention maybe applied to various wireless communication systems. Hereinafter, LTEincludes LTE and/or LTE-A.

The technical terms used herein are used to merely describe specificembodiments and should not be construed as limiting the presentinvention. Further, the technical terms used herein should be, unlessdefined otherwise, interpreted as having meanings generally understoodby those skilled in the art but not too broadly or too narrowly.Further, the technical terms used herein, which are determined not toexactly represent the spirit of the invention, should be replaced by orunderstood by such technical terms as being able to be exactlyunderstood by those skilled in the art. Further, the general terms usedherein should be interpreted in the context as defined in thedictionary, but not in an excessively narrowed manner.

The expression of the singular number in the present invention includesthe meaning of the plural number unless the meaning of the singularnumber is definitely different from that of the plural number in thecontext. In the following description, the term ‘include’ or ‘have’ mayrepresent the existence of a feature, a number, a step, an operation, acomponent, a part or the combination thereof described in the presentinvention, and may not exclude the existence or addition of anotherfeature, another number, another step, another operation, anothercomponent, another part or the combination thereof.

The terms ‘first’ and ‘second’ are used for the purpose of explanationabout various components, and the components are not limited to theterms ‘first’ and ‘second’. The terms ‘first’ and ‘second’ are only usedto distinguish one component from another component. For example, afirst component may be named as a second component without deviatingfrom the scope of the present invention.

It will be understood that when an element or layer is referred to asbeing “connected to” or “coupled to” another element or layer, it can bedirectly connected or coupled to the other element or layer orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element or layer, there are no intervening elementsor layers present.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.In describing the present invention, for ease of understanding, the samereference numerals are used to denote the same components throughout thedrawings, and repetitive description on the same components will beomitted. Detailed description on well-known arts which are determined tomake the gist of the invention unclear will be omitted. The accompanyingdrawings are provided to merely make the spirit of the invention readilyunderstood, but not should be intended to be limiting of the invention.It should be understood that the spirit of the invention may be expandedto its modifications, replacements or equivalents in addition to what isshown in the drawings.

As used herein, ‘base station’ generally refers to a fixed station thatcommunicates with a wireless device and may be denoted by other termssuch as eNB (evolved-NodeB), BTS (base transceiver system), or accesspoint.

As used herein, ‘user equipment (UE)’ may be stationary or mobile, andmay be denoted by other terms such as device, wireless device, terminal,MS (mobile station), UT (user terminal), SS (subscriber station), MT(mobile terminal) and etc.

FIG. 1 illustrates a wireless communication system.

As seen with reference to FIG. 1, the wireless communication systemincludes at least one base station (BS) 20. Each base station 20provides a communication service to specific geographical areas(generally, referred to as cells) 20 a, 20 b, and 20 c. The cell can befurther divided into a plurality of areas (sectors).

The UE generally belongs to one cell and the cell to which the UE belongis referred to as a serving cell. A base station that provides thecommunication service to the serving cell is referred to as a servingBS. Since the wireless communication system is a cellular system,another cell that neighbors to the serving cell is present. Another cellwhich neighbors to the serving cell is referred to a neighbor cell. Abase station that provides the communication service to the neighborcell is referred to as a neighbor BS. The serving cell and the neighborcell are relatively decided based on the UE.

Hereinafter, a downlink means communication from the base station 20 tothe UE1 10 and an uplink means communication from the UE 10 to the basestation 20. In the downlink, a transmitter may be a part of the basestation 20 and a receiver may be a part of the UE 10. In the uplink, thetransmitter may be a part of the UE 10 and the receiver may be a part ofthe base station 20.

Meanwhile, the wireless communication system may be generally dividedinto a frequency division duplex (FDD) type and a time division duplex(TDD) type. According to the FDD type, uplink transmission and downlinktransmission are achieved while occupying different frequency bands.According to the TDD type, the uplink transmission and the downlinktransmission are achieved at different time while occupying the samefrequency band. A channel response of the TDD type is substantiallyreciprocal. This means that a downlink channel response and an uplinkchannel response are approximately the same as each other in a givenfrequency area. Accordingly, in the TDD based wireless communicationsystem, the downlink channel response may be acquired from the uplinkchannel response. In the TDD type, since an entire frequency band istime-divided in the uplink transmission and the downlink transmission,the downlink transmission by the base station and the uplinktransmission by the terminal may not be performed simultaneously. In theTDD system in which the uplink transmission and the downlinktransmission are divided by the unit of a sub-frame, the uplinktransmission and the downlink transmission are performed in differentsub-frames.

Hereinafter, the LTE system will be described in detail.

FIG. 2 shows a downlink radio frame structure according to FDD of 3rdgeneration partnership project (3GPP) long term evolution (LTE).

The radio frame of FIG. 2 may be found in the section 5 of 3GPP TS36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation (Release 10)”.

The radio frame includes 10 sub-frames indexed 0 to 9. One sub-frameincludes two consecutive slots. Accordingly, the radio frame includes 20slots. The time taken for one sub-frame to be transmitted is denoted TTI(transmission time interval). For example, the length of one sub-framemay be 1 ms, and the length of one slot may be 0.5 ms.

The structure of the radio frame is for exemplary purposes only, andthus the number of sub-frames included in the radio frame or the numberof slots included in the sub-frame may change variously.

Meanwhile, one slot may include a plurality of orthogonal frequencydivision multiplexing (OFDM) symbols. The number of OFDM symbolsincluded in one slot may vary depending on a cyclic prefix (CP). Oneslot includes 7 OFDM symbols in case of a normal CP, and one slotincludes 6 OFDM symbols in case of an extended CP. Herein, since the3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in adownlink (DL), the OFDM symbol is only for expressing one symbol periodin a time domain, and there is no limitation in a multiple access schemeor terminologies. For example, the OFDM symbol may also be referred toas another terminology such as a single carrier frequency divisionmultiple access (SC-FDMA) symbol, a symbol period, etc.

FIG. 3 illustrates the architecture of a downlink radio frame accordingto TDD in 3GPP LTE.

For this, 3GPP TS 36.211 V10.4.0 (2011-23) “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, Ch. 4 may be referenced, and this is for TDD (timedivision duplex).

Sub-frames having index #1 and index #6 are denoted special sub-frames,and include a DwPTS (Downlink Pilot Time Slot: DwPTS), a GP (GuardPeriod) and an UpPTS (Uplink Pilot Time Slot). The DwPTS is used forinitial cell search, synchronization, or channel estimation in aterminal. The UpPTS is used for channel estimation in the base stationand for establishing uplink transmission sync of the terminal. The GP isa period for removing interference that arises on uplink due to amulti-path delay of a downlink signal between uplink and downlink.

In TDD, a DL (downlink) sub-frame and a UL (Uplink) co-exist in oneradio frame. Table 1 shows an example of configuration of a radio frame.

TABLE 1 Switch- UL-DL point Subframe index configuration periodicity 0 12 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 25 ms D S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S U U DD D D D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U D

‘D’ denotes a DL sub-frame, ‘U’ a UL sub-frame, and ‘S’ a specialsub-frame. When receiving a UL-DL configuration from the base station,the terminal may be aware of whether a sub-frame is a DL sub-frame or aUL sub-frame according to the configuration of the radio frame.

TABLE 2 Normal CP in downlink Extended CP in downlink UpPTS UpPTSSpecial Normal Normal Extended subframe CP in Extended CP in CP inconfiguration DwPTS uplink CP in uplink DwPTS uplink uplink 0  6592 * Ts2192 * Ts 2560 * Ts  7680 * Ts 2192 * Ts 2560 * Ts 1 19760 * Ts 20480 *Ts 2 21952 * Ts 23040 * Ts 3 24144 * Ts 25600 * Ts 4 26336 * Ts  7680 *Ts 5  6592 * Ts 4384 * Ts 5120 * ts 20480 * Ts 4384 * Ts 5120 * ts 619760 * Ts 23040 * Ts 7 21952 * Ts — 8 24144 * Ts —

FIG. 4 illustrates an example resource grid for one uplink or downlinkslot in 3GPP LTE.

Referring to FIG. 4, the uplink slot includes a plurality of OFDM(orthogonal frequency division multiplexing) symbols in the time domainand NRB resource blocks (RBs) in the frequency domain. For example, inthe LTE system, the number of resource blocks (RBs), i.e., NRB, may beone from 6 to 110.

The resource block is a unit of resource allocation and includes aplurality of sub-carriers in the frequency domain. For example, if oneslot includes seven OFDM symbols in the time domain and the resourceblock includes 12 sub-carriers in the frequency domain, one resourceblock may include 7×12 resource elements (REs).

Meanwhile, the number of sub-carriers in one OFDM symbol may be one of128, 256, 512, 1024, 1536, and 2048.

In 3GPP LTE, the resource grid for one uplink slot shown in FIG. 4 mayalso apply to the resource grid for the downlink slot.

FIG. 5 illustrates the architecture of a downlink sub-frame.

In FIG. 5, assuming the normal CP, one slot includes seven OFDM symbols,by way of example.

The DL (downlink) sub-frame is split into a control region and a dataregion in the time domain. The control region includes up to first threeOFDM symbols in the first slot of the sub-frame. However, the number ofOFDM symbols included in the control region may be changed. A PDCCH(physical downlink control channel) and other control channels areassigned to the control region, and a PDSCH is assigned to the dataregion.

The physical channels in 3GPP LTE may be classified into data channelssuch as PDSCH (physical downlink shared channel) and PUSCH (physicaluplink shared channel) and control channels such as PDCCH (physicaldownlink control channel), PCFICH (physical control format indicatorchannel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH(physical uplink control channel).

FIG. 6 illustrates the architecture of an uplink sub-frame in 3GPP LTE.

Referring to FIG. 6, the uplink sub-frame may be separated into acontrol region and a data region in the frequency domain. The controlregion is assigned a PUCCH (physical uplink control channel) fortransmission of uplink control information. The data region is assigneda PUSCH (physical uplink shared channel) for transmission of data (insome cases, control information may also be transmitted).

The PUCCH for one terminal is assigned in resource block (RB) pair inthe sub-frame. The resource blocks in the resource block pair take updifferent sub-carriers in each of the first and second slots. Thefrequency occupied by the resource blocks in the resource block pairassigned to the PUCCH is varied with respect to a slot boundary. This isreferred to as the RB pair assigned to the PUCCH having beenfrequency-hopped at the slot boundary.

The terminal may obtain a frequency diversity gain by transmittinguplink control information through different sub-carriers over time. mis a location index that indicates a logical frequency domain locationof a resource block pair assigned to the PUCCH in the sub-frame.

The uplink control information transmitted on the PUCCH includes an HARQ(hybrid automatic repeat request), an ACK (acknowledgement)/NACK(non-acknowledgement), a CQI (channel quality indicator) indicating adownlink channel state, and an SR (scheduling request) that is an uplinkradio resource allocation request.

The PUSCH is mapped with a UL-SCH that is a transport channel. Theuplink data transmitted on the PUSCH may be a transport block that is adata block for the UL-SCH transmitted for the TTI. The transport blockmay be user information. Or, the uplink data may be multiplexed data.The multiplexed data may be data obtained by multiplexing the transportblock for the UL-SCH and control information. For example, the controlinformation multiplexed with the data may include a CQI, a PMI(precoding matrix indicator), an HARQ, and an RI (rank indicator). Or,the uplink data may consist only of control information.

<Carrier Aggregation (CA)>

A carrier aggregation system is described hereinafter.

A carrier aggregation system aggregates a plurality of componentcarriers (CCs). A conventional definition of a cell is changed accordingto carrier aggregation. According to carrier aggregation, a cell maydenote a combination of a downlink component carrier and an uplinkcomponent carrier or a downlink component carrier alone.

Further, in carrier aggregation, cells may be divided into a primarycell, a secondary cell, and a serving cell. A primary cell denotes acell operating at a primary frequency, in which a UE performs an initialconnection establishment procedure or a connection reestablishmentprocedure with a BS or which is designated as a primary cell in ahandover procedure. A secondary cell denotes a cell operating at asecondary frequency, which is configured once RRC connection isestablished and is used to provide an additional radio resource.

As described above, the carrier aggregation system may support aplurality of component carriers (CCs), that is, a plurality of servingcells, unlike a single carrier system.

The carrier aggregation system may support cross-carrier scheduling.Cross-carrier scheduling is a scheduling method for performing resourceallocation for a PDSCH transmitted through a different component carrierthrough a PDCCH transmitted through a specific component carrier and/orresource allocation for a PUSCH transmitted through a component carrierdifferent from a component carrier basically linked with the specificcomponent carrier.

<Synchronization Signal>

In LTE/LTE-A systems, synchronization with a cell is obtained through asynchronization signal (SS) in a cell search process.

The synchronization signal is described in detail below with referenceto FIG. 7.

FIG. 7 illustrates a frame structure for the transmission of asynchronization signal in an FDD frame.

A slot number and a subframe number starts with 0. UE may perform timeand frequency synchronization based on a synchronization signal receivedfrom an eNodeB. In 3GPP LTE-A, a synchronization signal is used for cellsearch and may be divided into a primary synchronization signal (PSS)and a secondary synchronization signal (SSS). In 3GPP LTE-A, for asynchronization signal, reference may be made to Paragraph 6.11 of 3GPPTS V10.2.0 (2011-06).

A PSS is used to obtain 01-DM symbol synchronization or slotsynchronization and associated with a physical-layer cell identity(PCI). Furthermore, an SSS is used to obtain frame synchronization.Furthermore, an SSS is used to detect a CP length and to obtain aphysical layer cell group ID.

A synchronization signal may be transmitted in a subframe No. 0 and asubframe No. 5 several time by taking into consideration 4.6 ms, thatis, the length of a GSM (global system for mobile communication) framein order to facilitate inter-RAT (radio access technology) measurement.The boundary of the frame may be detected through an SSS. Morespecifically, in an FDD system, a PSS is transmitted in the last OFDMsymbol of a slot No. 1 or a slot No. 10, and an SSS is transmitted in anOFDM symbol right before a PSS.

A synchronization signal may send any one of a total of 504 physicalcell IDs through a combination of three PSSs and 168 SSSs. A PBCH(physical broadcast channel) is transmitted in the first 4 OFDM symbolsof the first slot. A synchronization signal and PBCH are transmittedwithin center 6 Rbs within a system bandwidth so that UE can detect ordemodulate the synchronization signal regardless of a transmissionbandwidth. A physical channel in which a PSS is transmitted is called aP-SCH, and a physical channel in which an SSS is transmitted is calledan S-SCH.

FIG. 8 illustrates an example of a frame structure for sending asynchronization signal in a TDD frame.

In a TDD frame, a PSS is transmitted in the third OFDM symbols of athird slot and thirteenth slot. An SSS is transmitted prior to threeOFDM symbols in OFDM symbols in which a PSS is transmitted. A PBCH istransmitted in the first 4 OFDM symbols of a second slot in the firstsubframe.

<Reference Signal>

A RS is described below.

In general, transmission information, for example, data is easilydistored and changed while it is transmitted through a radio channel.Accordingly, a reference signal is required in order to demodulate sucha transmission information without an error.

The reference signal is a signal known to both a transmitter and areceiver and is transmitted along with transmission information. Sincetransmission information transmitted by a transmitter experiences acorresponding channel for each transmission antenna or layer, areference signal may be allocated to each transmission antenna or layer.A reference signal for each transmission antenna or layer may beidentified using resources, such as a frequency and code. A referencesignal may be used for two purposes, that is, the demodulation andchannel estimation of transmission information.

A downlink reference signal may be divided into a cell-specificreference signal (CRS), an MBSFN (multimedia broadcast and multicastsingle frequency network) reference signal, a UE-specific referencesignal (UE-specific RS, URS), a positioning reference signal(positioning RS, PRS), and a CSI reference signal (CSI-RS). The CRS is areference signal transmitted to all UEs within a cell and also called acommon reference signal. The CRS may be used for the channel measurementof CQI feedback and the channel estimation of PDSCH. The MBSFN referencesignal may be transmitted in a subframe allocated for MBSFNtransmission. The URS is a reference signal received by a specific UE orspecific UE group within a cell and may be called a demodulationreference signal (DM-RS). The DM-RS is chiefly used for a specific UE orspecific UE group to perform data demodulation. The PRS may be used toestimate the location of UE. The CSI-RS is used for the channelestimation of the PDSCH of LTE-A UE. The CSI-RSs are deployed relativelysparsely in a frequency domain or time domain and may be punctured inthe data region of a common subframe or MBSFN subframe.

FIG. 9 illustrates one example of a pattern according to which a CRS ismapped to an RB in case a base station uses one antenna port.

Referring to FIG. 9, RO represents an RE to which a CRS transmitted byan antenna with a port number 0 of the base station is mapped.

A CRS is transmitted from all of downlink subframes within a cellsupporting PDSCH transmission. A CRS may be transmitted through antennaport 0 to 3.

A resource element (RE) allocated to the CRS of one antenna port may notbe used for transmission through another antenna port and has to be setto zero. Also, the CRS is transmitted only in the non-MBSFN area in anMBSFN (Multicast-Broadcast Single Frequency Network) subframe.

FIG. 10 illustrates measurement and a measurement report procedure.

In a mobile communication system, mobility support of the UE 100 isessential. Therefore, the UE 100 continuously measure the quality of aserving cell currently providing a service and the quality of itsneighboring cells. The UE 100 duly reports the measurement result to thenetwork, and the network provides the UE with optimal mobility throughhandover. Such measurement is often called RRM (Radio ResourceManagement).

Meanwhile, the UE 100 monitors downlink quality of the primary cell(Pcell) by using the CRS, which is called RLM (Radio Link Monitoring).To perform RLM, the UE 100 estimates downlink quality and compares theestimated downlink quality with Qout and Qin, for example. The thresholdvalue Qout is defined as the level at which downlink data may not bereceived reliably, which corresponds to 10% error of PDCCH transmissionif the PCFICH error is taken into account. The threshold value Qin isdefined as the level considerably reliable for downlink data comparedwith the Qout, which corresponds to 2% error of PDCCH transmission ifthe PCFICH error is taken into account.

As can be seen with reference to FIG. 10, if the serving cell 200 a andneighboring cells 200 b transmit CRSs (Cell-specific Reference Signals)respectively to the UE 100, the UE 100 performs measurement through theCRS and transmits the RRC measurement report message including themeasurement result to the serving cell 200 a.

At this time, the UE 100 may perform measurement by using the followingthree methods.

1) RSRP (Reference Signal Received Power): RSRP represents the averagereceived power of all REs carrying the CRS transmitted across the wholefrequency band. At this time, instead of using the CRS, the averagereceived power of all REs carrying a CRI RS may be measured.

2) RSSI (Received Signal Strength Indicator): RSSI represents receivedpower measured across the whole frequency band. RSSI includes all of asignal, interference, and thermal noise.

3) RSRQ (Reference Symbol Received Quality): RSRQ represents CQI and maybe determined by RSRP/RSSI according to measurement bandwidth orsub-band. In other words, RSRQ represents SINR (Signal-to-noiseInterference Ratio). Since RSRP does not provide sufficient mobilityinformation, RSRP or RSRQ may be used instead during handover or cellreselection process.

RSRQ may be obtained by RSSI/RSSP.

Meanwhile, to perform the measurement above, the UE 100 receivesmeasurement configuration (in what follows, it is also called‘measconfig’) information element (IE) from the serving cell 100 a. Amessage which includes the measconfig IE is denoted as a measurementconfiguration message. At this time, the measconfig IE may be receivedthrough an RRC connection re-establishment message. If the measurementresult satisfies a report condition within measurement configurationinformation, the UE reports the measurement result to the base station.A message which includes the measurement result is called a measurementreport message.

The measconfig IE may include measurement object information. Themeasurement object information is the information about an object forwhich the UE performs measurement. The measurement object includes atleast one of an intra-frequency measurement object which is ameasurement object within a cell, inter-frequency measurement objectwhich is a measurement object between cells, and inter-RAT measurementobject which is a measurement object of inter-RAT measurement. Forexample, an intra-frequency measurement object indicates a neighboringcell having the same frequency band with the serving cell,inter-frequency measurement object indicates a neighboring cell having adifferent frequency band from the serving cell, and inter-RATmeasurement object may indicate a neighboring cell using a different RATfrom that of the serving cell

More specifically, the measconfig IE includes information elements (IEs)as shown in the table below.

TABLE 3 MeasConfig ::= -- Measurement objects    measObjectToRemoveList   measObjectToAddModList -- Other parameters    measGapConfig

The measurement object IE may include measObjectToRemoveList whichcontains a list of measObjects to be removed and measObjectToAddModListcontaining a list to be added or modified.

Meanwhile, the measGapConfig is used to set up or release a measurementgap (MG).

The measurement gap (MG) is an interval in which identification of acell on a different inter-frequency from that of the serving cell andRSRP measurement are performed.

Meanwhile, the UE 100 receives radio resource configuration IE as shownin the figure.

The radio resource configuration dedicated IE is used forestablishing/modifying/releasing a radio bearer or modifying the MACstructure. The radio resource configuration IE includes subframe patterninformation. The subframe pattern information is the information about ameasurement resource restriction pattern on the time domain formeasuring RSRP and RSRQ of the serving cell (for example, the primarycell).

FIG. 11 illustrates one example of an RB to which a CSI-RS is mappedamong reference signals.

The LTE-A terminal uses the CSI-RS for channel estimation of the PDSCHand channel measurement for generating channel information. The CSI-RSis disposed sparsely in the frequency or time domain and may bepunctured in a normal subframe or in the data area of the MBSFNsubframe. In case the CSI-RS is required for the estimation of CSI, theUE may report CQI, PMI, and RI.

A CSI-RS is transmitted though one, two, four, or eight antenna ports.The antenna port used for this case is p=15; p=15, 16; p=15, . . . , 18;and p=15, . . . , 22, respectively. In other words, a CSI-RS may betransmitted through one, two, four, or eight antenna ports. A CSI-RS maybe defined only for the subcarrier interval of Δf=15 kHz. The clause6.10.5 of the 3GPP (3rd Generation Partnership Project) TS 36.211V10.1.0 (2011-03) “Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channelsand modulation (Release 8)” may be referenced for the CSI-RS.

To transmit a CSI-RS, a maximum of 32 different configurations may beproposed to reduce inter-cell interference (ICI) in a multi-cellenvironment including a heterogeneous network (HetNet) environment. TheCSI-RS configuration differs according to the number of antenna portswithin a cell and CP; and neighboring cells may have configurations asdifferent as possible from each other. Also, depending on framestructure, the CSI-RS configuration may be divided into the case whereit is applied to both of the FDD and TDD frames and the case where it isapplied only to the TDD frame. A plurality of CSI-RS configuration maybe used within one cell. For a UE which assumes non-zero power CSI-RS, 0or 1 CSI-RS configuration may be used while 0 or several CSI-RSconfigurations may be used for a UE which assumes zero power CSI-RS.

The table below shows a structure of CSI-RS in a normal CP.

TABLE 4 CSI-RS The number of CSI-RSs configuration 1 or 2 4 8 index (k′,l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 TDD and 0 (9,5) 0 (9, 5) 0 (9, 5) 0 FDD 1 (11, 2)  1 (11, 2)  1 (11, 2)  1 frame 2(9, 2) 1 (9, 2) 1 (9, 2) 1 3 (7, 2) 1 (7, 2) 1 (7, 2) 1 4 (9, 5) 1 (9,5) 1 (9, 5) 1 5 (8, 5) 0 (8, 5) 0 6 (10, 2)  1 (10, 2)  1 7 (8, 2) 1 (8,2) 1 8 (6, 2) 1 (6, 2) 1 9 (8, 5) 1 (8, 5) 1 10 (3, 5) 0 11 (2, 5) 0 12(5, 2) 1 13 (4, 2) 1 14 (3, 2) 1 15 (2, 2) 1 16 (1, 2) 1 17 (0, 2) 1 18(3, 5) 1 19 (2, 5) 1 TDD 20 (11, 1)  1 (11, 1)  1 (11, 1)  1 frame 21(9, 1) 1 (9, 1) 1 (9, 1) 1 22 (7, 1) 1 (7, 1) 1 (7, 1) 1 23 (10, 1)  1(10, 1)  1 24 (8, 1) 1 (8, 1) 1 25 (6, 1) 1 (6, 1) 1 26 (5, 1) 1 27(4, 1) 1 28 (3, 1) 1 29 (2, 1) 1 30 (1, 1) 1 31 (0, 1) 1

The table below shows a structure of CSI-RS in an extended CP.

TABLE 5 CSI-RS The number of CSI-RSs configuration 1 or 2 4 8 index (k′,l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 TDD and 0 (11,4)  0 (11, 4)  0 (11, 4)  0 FDD 1 (9, 4) 0 (9, 4) 0 (9, 4) 0 frame 2(10, 4)  1 (10, 4)  1 (10, 4)  1 3 (9, 4) 1 (9, 4) 1 (9, 4) 1 4 (5, 4) 0(5, 4) 0 5 (3, 4) 0 (3, 4) 0 6 (4, 4) 1 (4, 4) 1 7 (3, 4) 1 (3, 4) 1 8(8, 4) 0 9 (6, 4) 0 10 (2, 4) 0 11 (0, 4) 0 12 (7, 4) 1 13 (6, 4) 1 14(1, 4) 1 15 (0, 4) 1 16 (11, 1)  1 (11, 1)  1 (11, 1)  1 17 (10, 1)  1(10, 1)  1 (10, 1)  1 18 (9, 1) 1 (9, 1) 1 (9, 1) 1 19 (5, 1) 1 (5, 1) 120 (4, 1) 1 (4, 1) 1 TDD 21 (3, 1) 1 (3, 1) 1 frame 22 (8, 1) 1 23(7, 1) 1 24 (6, 1) 1 25 (2, 1) 1 26 (1, 1) 1 27 (0, 1) 1

The UE may transmit the CSI-RS only in a downlink slot satisfying thecondition of n_(s) mode 2 shown in the table above. Also, the UE doesnot transmit a CSI-RS for a special frame of the TDD frame and thesubframe for which transmission of the CSI-RS collides with asynchronization signal, PBCH (Physical Broadcast Channel), and systeminformation block type 1 (SystemInformationBLockType 1) or for thesubframe to which a paging message is transmitted. Also, for a set Swhere S={15}, S={15, 16}, S={17, 18}, or S={21, 22}, the resourceelement to which the CSI-RS of one antenna port is transmitted is notused for transmission of the PDSCH or transmission of the CSI-RS of adifferent antenna port.

Meanwhile, FIG. 11 shows resource elements used for the CSI-RS when theCSI-RS configuration index is 0 in the case of a normal CP. Rprepresents a resource element used for transmission of a CSI-RS on theantenna port p. Referring to the figure, the CSI-RS for the antenna port15 and 16 is transmitted through the resource element corresponding tothe third subcarrier (subcarrier index 2) of the sixth and the seventhOFDM symbol (OFDM symbol index 5 and 6) of the first slot. The CSI-RSfor the antenna port 17 and 18 is transmitted through the resourceelement corresponding to the ninth subcarrier (subcarrier index 8) ofthe sixth and seventh OFDM symbol (OFDM symbol index 5 and 6) of thefirst slot. The CSI-RS for the antenna port 19 and 20 is transmittedthrough the same resource element through which the CSI-RS for theantenna port 15 and 16 is transmitted while the CSI-RS for the antennaport 21 and 22 is transmitted through the same resource element throughwhich the CSI-RS for the antenna port 17 and 18 is transmitted.

If a CSI-RS is transmitted to the UE through 8 antenna ports, the UEwill receive an RB to which R15 to R22 are mapped. In other words, theUE will receive the CSI-RS having a specific pattern.

Meanwhile, descriptions will be given with respect to small cells.

<Introduction of Small Cell>

Meanwhile, in the next-generation mobile communication system, smallcells having small cell coverage are expected to be added into theexisting cell coverage and to deal with much more traffic. Since theconventional cell provides coverage larger than that of the small cell,it is also called a macro cell. In what follows, descriptions will begiven with reference to FIG. 7.

FIG. 12 illustrates a heterogeneous network in which a macro cell andsmall cells are mixed, which may evolve to the next-generationcommunication system.

Referring to FIG. 12, a macro cell due to an existing eNB 200 forms aheterogeneous network being overlapped with small cells due to one ormore small eNBs 300 a, 300 b, 300 c, 300 d. Since the existing eNBprovides larger coverage than the small eNBs, it is also called a macroeNodeB (or MeNB). In this document, the term of macro cell and the termof macro eNodeB will be used interchangeably. A UE connected to themacro cell 200 may be called a macro UE. The macro UE receives adownlink signal from the MeNB and transmits an uplink signal to theMeNB.

In the heterogeneous network as described above designate the macro cellas the primary cell (Pcell) and the small cell as the secondary cell(Scell), thereby filling up the coverage gap inherent in the macro cell.Also, by designating the small cell as the Pcell and the macro cell asthe secondary cell, the overall performance may be boosted.

On the other hand, according as small cells are disposed, inter-cellinterference may become more severe. To solve this problem, as shown inthe figure, the coverage of the small cell may be reduced depending onthe situation. Or the small cell may be turned off or on again dependingon the situation.

FIG. 13 illustrates a situation in which small cells are distributeddensely.

Referring to FIG. 13, small cells are distributed densely within thecoverage of a macro cell. In this situation, the UE 100 may find itdifficult to detect the small cells quickly. In particular, as describedabove, detection of a cell is performed through reception of PSS/SSS.However, if a plurality of small cells attempts to transmit the PSS/SSSat the same time, namely on the 0-th and fifth subframe, the UE 100 mayhave a difficulty in receiving the PSS/SSS simultaneously. Moreover,since interference is caused as small cells transmit the PSS/SSSsimultaneously on the 0-th and the fifth subframe, the UE may notreceive the PSS/SSS properly.

To solve the problem above, a small cell may transmit a new discoverysignal (DS) in addition to the existing PSS/SSS. In what follows,descriptions will be given with reference to FIG. 14.

FIG. 14 illustrates an example in which small cells transmit a discoverysignal.

As shown in FIG. 14, in order to enable the UE to detect small cellsefficiently, small cells may transmit a new discovery signal (DS) inaddition to the existing PSS/SSS. A small cell which is in the turn-offstate may also transmit the discovery signal periodically.

The DS may be called a discovery reference signal (DRS). Accordingly,the UE has to perform a cell search procedure or cell detectionprocedure using the DS in addition to the existing PSS/SSS.

FIG. 15 illustrates a discovery signal.

As shown in FIG. 15, a DS may be a combination of the following signals:

-   -   CRS of the antenna port 0 during DwPTS of all of downlink        subframes and special subframe,    -   PSS on the first subframe within the period for the case of        frame type 1 for the FDD or PSS on the second subframe within        the period for the case of frame type 2 for the TDD,    -   SSS on the first subframe within the period, and    -   CSI-RS of non-zero power on zero or one or more subframes within        the period.

In other words, the DS may be a combination of CRS, SS (namely PSS andSSS), and CSI-RS.

Meanwhile, as shown in FIG. 15, the occasion interval of a DS may becomposed of by the following:

-   -   one to five consecutive subframes for the case of frame type 1        for the FDD, and    -   two to five consecutive subframes for the case of subframes for        the TDD.

Meanwhile, the UE may receive Discovery Signal Measurement TimingConfiguration (DMTC) which is the timing information for measurementbased on the discovery signal from the eNB. The DMTC may be received inthe form of MeasDS-Config field as shown in the table below. TheMeasDS-Config may be received by being included in the measurementobjects shown in Table 3. In other words, the MeasDS-Config fielddefining the DMTC may be received by being included in the measurementobjects within the MeasConfig of Table 3.

The UE does not assume that a discovery signal is transmitted on thesubframe not defined in the DMTC.

TABLE 6 Description of MeasDS-Config field csi-RS-IndividualOffsetIndividual CSI-RS offset applicable to a specific CSI-RS resourcedmtc-PeriodOffset dmtc-PeriodOffset represents DMTC periodicity(dmtc-periodicity) and DMTC offset (dmtc-Offset) for a given frequency.The DMTC period may be 40 ms, 80 ms, or 160 ms. The DMTC offset isexpressed by the number of subframes. The DMTC occasion interval is 6ms. ds-OccasionDuration ds-OccasionDuration represents the occasioninterval of a discovery signal with respect to a given frequency. Theoccasion interval of a discovery signal is common to all the cellstransmitting a discovery signal at the given frequency. physCellIdphyCellId represents a physical cell ID. The UE assumes that CSI-RScorresponding to the physical cell ID and PSS/SSS/CRS correspond toaverage delay and quasi co-location with respect to Doppler shift.resourceConfig resourceConfig represents CSI-RS configuration.subframeOffset subframeOffset represents a subframe offset between SSSof a cell identified by the physical cell ID within the discovery signaloccasion interval and the CSI-RS resource.

In the table above, the dmtc-Periodicity is a measurement period,indicating one of 40 ms, 80 ms, or 160 ms. For example, the UE mayperform measurement based on the discovery signal (DS) every 160 ms. Theds-OccasionDuration is the occasion interval of the discovery signal; inthe case of FDD, it indicates the number of appropriate subframes among1 to 5 consecutive subframes, and in the case of TDD, it indicates thenumber of appropriate subframes among 2 to 5 consecutive subframes. TheDMTC occasion interval is a measurement performance interval. Forexample, in case the dmtc-Periodicity is 160 ms, and the DMTC occasioninterval is 6 ms, the UE measures the discovery signal from a small cellfor the period of 6 ms every 160 ms.

Meanwhile, descriptions about the small cell given so far may besummarized as follows.

For identification and measurement of a small cell, a discovery signaland a measurement interval have been newly defined. To identify andmeasure a small cell, the UE uses DMTC (Discovery Signal MeasurementTiming Configuration) information received from the serving cell. Theoccasion interval of the DMTC is 6 ms, and period of the DMTC is one of40 ms, 80 ms, and 160 ms. In other words, the UE performs the operationof detecting and measuring a small cell within the interval of 6 ms,which is the DMTC occasion interval. According to the occasion intervalof the discovery signal, in the case of FDD, the DS may be received onthe 1 to 5 consecutive subframes while the DS may be received on the 2to 5 consecutive subframes. Among the subframes, SSS and CRS arereceived on the first subframe, and for the case of FDD, PSS isadditionally received. In the case of TDD, PSS is received on the secondsubframe among the subframes.

The small cell may be turned on/off; since the UE is unable to knowbeforehand as to whether the small cell is in the on-state or off-state,irrespective of the small cell's state (either on or off-state), the UEalways performs the operation of detecting and measuring a cell by usingthe discovery signal.

The purpose of the discovery signal is acquisition of synchronizationthrough PSS/SSS, RSRP measurement based on the CRS, acquisition ofCSI-RS, and RSRP measurement based on the CSI-RS.

The occasion interval of the discovery signal includes 1 to 5consecutive subframes in the case of FDD and includes 2 to 5 subframesin the case of TDD.

As described above, SSS/CRS in the occasion interval of the discoverysignal is received on the first subframe, and the CSI-RS is received atthe position separated by the subframeoffset value of Table 3 from theSSS subframe.

FIG. 16 illustrates a measurement process based on a discovery signal.

As shown in FIG. 16, the UE 100 receives measurement configurationinformation from a serving cell. The measurement configurationinformation may be the measconfig as shown in Table 3. The measurementconfiguration information, namely measurement object within themeasconfig may include measurement timing configuration (DMTC) based onthe discovery signal for a neighboring small cell, namely MeasDS-Config.

At this time, the DMTC, namely MeasDS-Config may includedmtc-Periodicity, DMTC occasion interval, and information about theoccasion interval of the discovery signal, namely ds-OccasionDuration.

Afterwards, the UE 100 performs measurement of the discovery signal ofthe small cell during the DMTC occasion interval, namely for 6 ms everydmtc-Periodicity, namely 40 ms, 80 ms, or 160 ms.

It should be noted, however, that research on how many times the UE 100has to perform measurement to obtain desired measurement accuracy hasnot been conducted yet. In other words, it is uncertain how many timesduring the total measurement period the UE has to perform measurement toobtain the desired measurement accuracy. For example, supposedmtc-Periodicity is 160 ms and the UE 100 performs measurement every 160ms. In this case it is unclear how many times (for example, i times)during the total period of measurement (i*160 ms) the UE has to performmeasurement to obtain desired accuracy.

DISCLOSURE OF THE PRESENT INVENTION

Therefore, this document aims to provide a method for solving theproblem above.

I. First Disclosure of the Present Invention

The first disclosure of the present invention specifies according to asimulation study as to how long (i*160 ms) the UE has to performmeasurement based on the discovery signal with respect to a small cell.

I-1. Simulation Environment

I-1-1. Simulation Environment for RSRP Measurement Based on the CRS Outof Discovery Signal

It is assumed that the UE is capable of performing based on the CRS outof the discovery signal during the occasion interval of the discoverysignal for all of downlink subframes and DwPTS.

Also, the following are the simulation parameters.

1) Side conditions

The SNR condition as shown below may be re-used for the conventional CRSmeasurement.

SNR: {−10, −8, −6, −3, 0} dB

2) Occasion interval of discovery signal

It is assumed that the occasion interval of a discovery signal in anarbitrary small cell is 1, 3, or 5 subframes.

At this time, it is assumed that all of downlink subframes include aCRS.

If dmtc-Periodicity representing a measurement period is denoted by Mms, M is 160.

3) Measurement bandwidth: {6 RBs, 25 RBs, 50 RBs}

4) Total measurement interval: i*160 ms, i={1, 3, 5}

The table below summarizes the assumptions and conditions describedabove.

TABLE 7 parameter Value Description SNR {−10, −8, −6, −3, 0} dBMeasurement bandwidth {6 RBs, 25 RBs, 50 RBs} The number of transmitting{1} (Tx) antennas The number of receiving 2 (Rx) antenna Antennacorrelation Low DMTC period (M) 160  Measurement is performed every M msOccasion interval (N) of 1 Discovery discovery signal signal occurs at Nsubframes Measurement interval i * 160 ms, i = {1, 3, 5} L3 filteringDisable DRX (discontinuous OFF reception) Propagation condition AWGN,EPA5, ETU30 CP length Normal AWGN stands for Additive White GaussianNoise. EPA5 denotes Doppler frequency of 5 MHz for the ExtendedPdestrian A model. ETU30 denotes Doppler frequency of 30 MHz for theExtended Typical Urban model.

I-1-2. Simulation Environment for RSRP Measurement Based on the CSI-RSOut of Discovery Signal

It is assumed that the UE receives a CSI-RS in case the correspondingCSI-RS is included in the discovery signal (DS).

Also, the following are the simulation parameters.

1) Side conditions: SNR: {−4, −3, 0, 3} dB

2) Occasion interval of discovery signal

1, 3, or 5 subframes.

DMTC period is M ms, where M is 160.

3) Transmission of CSI-RS

It is assumed that during the occasion interval of discovery signal(DS), the UE receives a CSI-RS from at least one subframe.

4) Measurement bandwidth: {6 RBs, 25 RBs, 50 RBs}

5) Measurement interval: i*160 ms, i={1, 3, 5}

The table below summarizes the assumptions and conditions describedabove.

TABLE 8 parameter Value Description SNR {−4, −3, 0, 3} dB Measurementbandwidth {6 RBs, 25 RBs, 50 RBs} The number of transmitting 1 (Tx)antennas The number of receiving (Rx) 2 antenna Antenna correlation LowCSI-RS Antenna port {15} DMTC period (M) 160  Measurement is performedevery M ms Occasion interval (N) of 1, 3, or 5 subframes discoverysignal CSI-RS transmission 1 subframe by default CSI-RS configurationCSI-RS configuration index 1 Measurement interval i * 160 ms, i = {1, 3,5} L3 filtering Disable DRX OFF Propagation condition AWGN, EPA5, ETU30CP length Normal

I-2. Simulation Result

The curvature of a cumulative distribution function (CDF) is used as aperformance metric to specify the following.

CRS-based delta RSRP=(measure CRS-based RSRP−CRS-based ideal RSRP) [dB]

CSI-RS based delta RSRP=(measured CSI-RS based RSRP−CSI-RS based idealRSRP) [dB]

The experimental result below is based on the condition that theoccasion interval of the discovery signal ranges one subframe.

I-2-1. Simulation Result of RSRP Measurement Based on the CRS Out ofDiscovery Signal

First, in case the measurement bandwidth comprises 6 RBs, simulationresults of CRS-based delta RSRP for AGWN, ETA5, and ETU30 are asfollows.

FIGS. 17a to 17c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 6 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 17a to 17c , Table 9 summarizes the simulation resultof CRS-based delta RSRP for AGWN, ETA5, and ETU30 when the measurementbandwidth comprises 6 RBs.

Even considering the RF defect of about 3 dB with respect to theabsolute RSRP and the relative RSRP of 1 dB, the values not satisfyingthe current inter-frequency CRS-based requirements are shown beingunderlined in the table below.

TABLE 9 Reference Measurement Relative Propagation SNR interval accuracycondition [dB] (i * 160 ms), i 50% 5% 95% [5%-50%, 95%-50%] AWGN −10 11.82 0.15 3.37 −1.67 1.55 3 1.60 0.67 2.55 −0.94 0.95 5 1.52 0.81 2.28−0.71 0.76 −8 1 1.44 0.08 2.77 −1.36 1.33 3 1.27 0.50 2.06 −0.77 0.79 51.21 0.62 1.82 −0.59 0.62 −6 1 1.16 0.07 2.21 −1.10 1.05 3 1.02 0.381.64 −0.64 0.62 5 0.96 0.48 1.46 −0.48 0.49 −3 1 0.75 −0.05 1.52 −0.800.76 3 0.62 0.17 1.07 −0.45 0.45 5 0.57 0.23 0.94 −0.34 0.36 0 1 0.33−0.27 0.83 −0.60 0.50 3 0.22 −0.11 0.54 −0.33 0.32 5 0.19 −0.07 0.44−0.26 0.26 EPA5 −10 1 2.08 −3.16 6.48 −5.23 4.40 3 2.09 −0.95 4.78 −3.032.70 5 1.99 −0.29 4.15 −2.28 2.16 −8 1 1.82 −3.93 6.24 −5.74 4.42 3 1.75−1.36 4.56 −3.11 2.81 5 1.70 −0.59 3.92 −2.29 2.21 −6 1 1.58 −4.58 5.95−6.16 4.36 3 1.47 −1.69 4.26 −3.17 2.79 5 1.41 −0.90 3.67 −2.31 2.26 −31 1.24 −5.01 5.48 −6.25 4.24 3 1.12 −1.98 3.81 −3.09 2.70 5 1.03 −1.273.19 −2.30 2.16 0 1 0.86 −5.39 4.87 −6.25 4.01 3 0.66 −2.37 3.25 −3.032.58 5 0.59 −1.65 2.65 −2.24 2.06 ETU30 −10 1 1.47 −2.49 5.41 −3.95 3.943 1.40 −0.90 3.76 −2.30 2.36 5 1.32 −0.46 3.23 −1.77 1.92 −8 1 1.16−3.19 5.15 −4.35 3.99 3 1.09 −1.36 3.46 −2.45 2.37 5 0.98 −0.86 2.91−1.84 1.93 −6 1 0.86 −3.63 4.86 −4.49 4.00 3 0.81 −1.75 3.17 −2.56 2.365 0.69 −1.27 2.62 −1.97 1.92 −3 1 0.48 −4.20 4.41 −4.68 3.93 3 0.38−2.21 2.72 −2.59 2.34 5 0.27 −1.66 2.18 −1.93 1.91 0 1 0.10 −4.70 3.86−4.80 3.76 3 −0.05 −2.53 2.20 −2.48 2.25 5 −0.16 −2.09 1.67 −1.92 1.83

Next, simulation results of CRS-based delta RSRP for AGWN, ETA5, andETU30 when measurement bandwidth comprises 25 RBs are described below.

FIGS. 18a to 18c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 25 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 18a to 18c , Table 10 summarizes the simulation resultof CRS-based delta RSRP for AGWN, ETA5, and ETU30 when the measurementbandwidth comprises 6 RBs.

Even considering the RF defect of about 3 dB with respect to theabsolute RSRP and the relative RSRP of 1 dB, the values not satisfyingthe current inter-frequency CRS-based requirements are shown beingunderlined in the table below. In the table below, the values closer to0 indicate that more requirements are satisfied, and the values fartherfrom 0 indicate that less requirements are satisfied.

TABLE 10 Reference Measurement Propagation SNR interval Relativeaccuracy condition [dB] (i*160 ms), i 50% 5% 95% [5%-50%, 95%-50%] AWGN−10 1 0.24 −0.65 1.11 −0.89 0.87 3 0.10 −0.40 0.64 −0.51 0.54 5 0.06−0.34 0.48 −0.41 0.42 −8 1 0.13 −0.56 0.84 −0.69 0.71 3 0.03 −0.38 0.44−0.41 0.41 5 −0.01 −0.32 0.31 −0.31 0.33 −6 1 0.22 −0.35 0.80 −0.56 0.593 0.13 −0.19 0.47 −0.33 0.34 5 0.10 −0.15 0.37 −0.25 0.26 −3 1 0.27−0.13 0.68 −0.40 0.41 3 0.21 −0.02 0.45 −0.23 0.24 5 0.19 0.00 0.38−0.19 0.19 0 1 0.21 −0.06 0.49 −0.27 0.28 3 0.17 0.02 0.33 −0.15 0.17 50.15 0.04 0.28 −0.12 0.12 EPA5 −10 1 0.79 −4.12 5.05 −4.92 4.25 3 0.72−1.93 3.50 −2.65 2.78 5 0.65 −1.38 2.90 −2.02 2.25 −8 1 0.82 −4.09 5.06−4.91 4.24 3 0.74 −1.90 3.50 −2.64 2.76 5 0.67 −1.33 2.92 −2.00 2.26 −61 0.87 −4.04 5.10 −4.91 4.23 3 0.77 −1.85 3.54 −2.61 2.77 5 0.69 −1.252.95 −1.94 2.26 −3 1 0.92 −3.97 5.10 −4.89 4.18 3 0.81 −1.75 3.56 −2.572.75 5 0.74 −1.20 2.97 −1.94 2.23 0 1 0.91 −3.86 5.02 −4.77 4.11 3 0.79−1.73 3.49 −2.52 2.70 5 0.72 −1.18 2.91 −1.90 2.19 ETU30 −10 1 −0.16−3.80 3.09 −3.64 3.24 3 −0.33 −2.33 1.63 −2.00 1.96 5 −0.44 −1.98 1.14−1.54 1.57 −8 1 0.07 −3.44 3.18 −3.51 3.11 3 −0.13 −2.06 1.74 −1.93 1.885 −0.22 −1.73 1.28 −1.51 1.50 −6 1 0.22 −3.02 3.17 −3.24 2.95 3 0.03−1.78 1.80 −1.81 1.77 5 −0.07 −1.49 1.33 −1.42 1.40 −3 1 0.14 −2.96 3.05−3.10 2.90 3 −0.05 −1.78 1.68 −1.74 1.72 5 −0.13 −1.49 1.23 −1.36 1.36 01 −0.01 −3.03 2.84 −3.02 2.85 3 −0.20 −1.91 1.49 −1.71 1.69 5 −0.29−1.63 1.03 −1.34 1.32

Next, simulation results of CRS-based delta RSRP for AGWN, ETA5, andETU30 when measurement bandwidth comprises 50 RBs are described below.

FIGS. 19a to 19c illustrate CRS-based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 50 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 19a to 19c , Table 11 summarizes the simulation resultof CRS-based delta RSRP for AGWN, ETA5, and ETU30 when the measurementbandwidth comprises 6 RBs.

Even considering the RF defect of about 3 dB with respect to theabsolute RSRP and the relative RSRP of 1 dB, the values not satisfyingthe current inter-frequency CRS-based requirements are shown beingunderlined in the table below.

TABLE 11 Reference Measurement Propagation SNR interval Relativeaccuracy condition [dB] (i*160 ms), i 50% 5% 95% [5%-50%, 95%-50%] AWGN−10 1 0.53 −0.06 1.14 −0.59 0.61 3 0.44 0.09 0.79 −0.35 0.35 5 0.41 0.140.69 −0.27 0.28 −8 1 0.39 −0.08 0.90 −0.47 0.51 3 0.33 0.04 0.62 −0.290.30 5 0.30 0.08 0.53 −0.22 0.23 −6 1 0.29 −0.09 0.70 −0.39 0.41 3 0.230.02 0.47 −0.22 0.24 5 0.21 0.05 0.40 −0.16 0.18 −3 1 0.16 −0.11 0.45−0.27 0.29 3 0.12 −0.04 0.29 −0.16 0.17 5 0.11 −0.02 0.23 −0.12 0.13 0 10.07 −0.12 0.27 −0.18 0.20 3 0.04 −0.07 0.15 −0.11 0.12 5 0.03 −0.060.12 −0.08 0.09 EPA5 −10 1 1.00 −3.15 4.98 −4.15 3.98 3 0.91 −1.38 3.50−2.29 2.59 5 0.85 −0.91 2.89 −1.76 2.04 −8 1 0.93 −3.28 4.91 −4.22 3.973 0.84 −1.51 3.44 −2.35 2.60 5 0.77 −1.04 2.84 −1.81 2.07 −6 1 0.86−3.43 4.87 −4.30 4.01 3 0.76 −1.59 3.39 −2.35 2.63 5 0.70 −1.12 2.80−1.82 2.10 −3 1 0.78 −3.58 4.80 −4.35 4.02 3 0.67 −1.72 3.32 −2.38 2.655 0.61 −1.22 2.72 −1.83 2.11 0 1 0.70 −3.68 4.71 −4.38 4.01 3 0.59 −1.803.23 −2.39 2.64 5 0.53 −1.31 2.63 −1.84 2.09 ETU30 −10 1 0.53 −1.84 2.84−2.37 2.31 3 0.34 −0.98 1.67 −1.33 1.32 5 0.27 −0.77 1.31 −1.05 1.03 −81 0.41 −1.95 2.73 −2.36 2.32 3 0.21 −1.10 1.55 −1.31 1.34 5 0.13 −0.921.18 −1.05 1.05 −6 1 0.28 −2.09 2.60 −2.37 2.32 3 0.09 −1.25 1.42 −1.341.33 5 0.02 −1.05 1.07 −1.07 1.05 −3 1 0.10 −2.31 2.43 −2.41 2.33 3−0.10 −1.45 1.26 −1.36 1.36 5 −0.17 −1.25 0.90 −1.08 1.06 0 1 −0.10−2.49 2.23 −2.39 2.34 3 −0.30 −1.65 1.04 −1.36 1.34 5 −0.37 −1.45 0.68−1.08 1.05

Meanwhile, absolute accuracy and relative accuracy required for RSRPmeasurement are shown in Table 12 below.

TABLE 12 Intra-frequency Inter-frequency RSRP RSRQ RSRP RSRQ SNRAbsolute Relative Absolute Relative Absolute Relative Absolute Relative−6 ±6 ±3 ±3.5 N/A ±6 ±6 ±3.5 ±4 −3 ±2 ±2.5 ±2.5 ±3

Considering from Table 12 that absolute accuracy and relative accuracyrequired for inter-frequency RSRP measurement is ±6 dB for SNR −6 dB and−3 dB, simulation results of Table 9 to Table 11 may be summarized asfollows.

1) Summary 1: under AWGN when measurement bandwidth comprises 6 RBs, 25RBs, and 50 RBs, for SNR −6 dB and −3 dB, CRS-based absolute measurementaccuracy and relative measurement accuracy may satisfy the currentrequirement of ±6 dB from one measurement during 160 ms.

2) Summary 2: under EPA5 when measurement bandwidth comprises 25 RBs and50 RBs, for SNR −6 dB and −3 dB, CRS-based absolute measurement accuracymay satisfy the current requirement of ±6 dB from 160 ms*5 measurements.

3) Summary 3: under EPA5 when measurement bandwidth comprises 6 RBs, forSNR −6 dB and −3 dB, CRS-based relative measurement accuracy may satisfythe current requirement of ±6 dB from 160 ms*3 measurements. And underEPA5 when measurement bandwidth comprises 25 RBs and 50 RBs, for SNR −6dB and −3 dB, CRS-based relative measurement accuracy may satisfy thecurrent requirement of ±6 dB from 160 ms*1 measurement.

4) Summary 4: under ETU30 when measurement bandwidth comprises 6 RBs,for SNR −6 dB and −3 dB, CRS-based absolute measurement accuracy maysatisfy the current requirement of ±6 dB from 160 ms*3 or 160 ms*5measurements.

5) Summary 5: under ETU30 when measurement bandwidth comprises 25 RBs,for SNR −6 dB and −3 dB, CRS-based absolute measurement accuracy maysatisfy the current requirement of ±6 dB from 160 ms*3 measurements. Andunder ETU30 when measurement bandwidth comprises 50 RBs, for SNR −6 dBand −3 dB, CRS-based absolute measurement accuracy may satisfy thecurrent requirement of ±6 dB from 160 ms*1 measurement.

6) Summary 6: under ETU30 when measurement bandwidth comprises 6 RBs, 25RBs, and 50 RBs, for SNR −6 dB and −3 dB, CRS-based relative measurementaccuracy may satisfy the current requirement of ±6 dB from 160 ms*1measurement.

The summary above provides the minimum required measurement interval(160 ms*i times) for SNR −6 dB and −3 dB to satisfy the currentrequirements for CRS-based RSRP measurement.

The above result may be shown again in the table below.

TABLE 13 SNR i * 160 ms(i) (−6 dB/−3 dB) 6 RB 25 RB 50 RB AWGN 1 1 1EPA5 >5 5 5 ETU30 5 3 1

I-2-2. Simulation Result of RSRP Measurement Based on the CSI-RS Out ofDiscovery Signal

First, the following show the simulation results of CSI-RS based deltaRSRP for AGWN, ETA5, and ETU 30 when the measurement bandwidth comprises6 RBs.

FIGS. 20a to 20c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 6 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 20a to 20c , Table 14 summarizes the simulation resultof CSI-RS based delta RSRP for AGWN, ETA5, and ETU30 when themeasurement bandwidth comprises 6 RBs.

TABLE 14 Measurement Propagation SNR interval 2RE condition [dB] (i*160ms), i 50% 5% 95% [5-50%, 95-50%] AWGN −4 1 2.67 −0.82 5.33 −3.49 2.66 32.35 0.46 4.07 −1.89 1.72 5 2.22 0.78 3.60 −1.44 1.38 −3 1 2.27 −1.084.78 −3.35 2.51 3 1.92 0.12 3.52 −1.80 1.60 5 1.79 0.44 3.06 −1.36 1.270 1 1.37 −1.33 3.44 −2.69 2.07 3 1.05 −0.41 2.38 −1.46 1.33 5 0.96 −0.192.00 −1.15 1.04 3 1 0.82 −1.05 2.41 −1.87 1.59 3 0.59 −0.49 1.57 −1.080.98 5 0.50 −0.33 1.30 −0.83 0.80 EPA5 −4 1 2.74 −1.62 6.76 −4.36 4.02 32.70 0.15 5.14 −2.54 2.45 5 2.61 0.67 4.51 −1.94 1.90 −3 1 2.28 −2.166.59 −4.44 4.31 3 2.27 −0.33 4.90 −2.59 2.63 5 2.20 0.19 4.28 −2.02 2.080 1 1.43 −3.91 6.09 −5.34 4.66 3 1.46 −1.65 4.43 −3.11 2.98 5 1.41 −0.953.79 −2.36 2.37 3 1 1.14 −5.10 5.96 −6.24 4.82 3 1.18 −2.27 4.26 −3.443.09 5 1.13 −1.43 3.58 −2.56 2.45 ETU30 −4 1 2.88 −1.17 6.55 −4.05 3.673 2.75 0.40 5.02 −2.34 2.27 5 2.65 0.84 4.46 −1.81 1.81 −3 1 2.48 −1.886.22 −4.36 3.74 3 2.37 −0.11 4.61 −2.48 2.23 5 2.27 0.33 4.06 −1.94 1.790 1 1.65 −3.01 5.81 −4.66 4.16 3 1.58 −0.95 4.10 −2.54 2.52 5 1.49 −0.523.55 −2.01 2.05 3 1 1.34 −3.33 5.45 −4.67 4.11 3 1.27 −1.36 3.79 −2.632.52 5 1.18 −0.90 3.22 −2.07 2.05

Next, the following show the simulation results of CSI-RS based deltaRSRP for AGWN, ETA5, and ETU 30 when the measurement bandwidth comprises25 RBs.

FIGS. 21a to 21c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 25 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 21a to 21c , Table 15 summarizes the simulation resultof CSI-RS based delta RSRP for AGWN, ETA5, and ETU30 when themeasurement bandwidth comprises 25 RBs.

TABLE 15 Measurement Propagation SNR interval 2RE condition [dB] (i*160ms), i 50% 5% 95% [5-50%, 95-50%] AWGN −4 1 1.26 −1.20 3.20 −2.47 1.93 30.99 −0.37 2.21 −1.37 1.21 5 0.89 −0.16 1.83 −1.05 0.94 −3 1 1.11 −1.092.72 −2.20 1.61 3 0.79 −0.40 1.85 −1.19 1.06 5 0.69 −0.22 1.55 −0.910.87 0 1 0.63 −0.73 1.86 −1.36 1.23 3 0.43 −0.34 1.18 −0.77 0.75 5 0.36−0.22 0.96 −0.58 0.59 3 1 0.41 −0.51 1.29 −0.92 0.88 3 0.27 −0.27 0.78−0.54 0.51 5 0.23 −0.20 0.62 −0.43 0.39 EPA5 −4 1 1.51 −2.88 5.45 −4.393.93 3 1.39 −1.01 3.92 −2.40 2.53 5 1.30 −0.57 3.33 −1.87 2.04 −3 1 1.34−3.07 5.35 −4.41 4.02 3 1.23 −1.28 3.80 −2.51 2.57 5 1.15 −0.77 3.19−1.92 2.04 0 1 1.06 −3.92 5.18 −4.98 4.12 3 0.93 −1.66 3.62 −2.59 2.70 50.87 −1.13 3.01 −2.01 2.14 3 1 0.92 −4.00 5.12 −4.93 4.20 3 0.82 −1.773.61 −2.58 2.79 5 0.74 −1.21 3.00 −1.94 2.26 ETU30 −4 1 1.45 −2.04 4.37−3.49 2.93 3 1.23 −0.70 2.98 −1.93 1.74 5 1.12 −0.36 2.52 −1.48 1.40 −31 1.29 −2.18 4.18 −3.47 2.89 3 1.05 −0.87 2.82 −1.92 1.77 5 0.93 −0.542.38 −1.47 1.44 0 1 0.96 −2.31 3.80 −3.27 2.84 3 0.75 −1.06 2.48 −1.821.73 5 0.65 −0.72 2.04 −1.37 1.39 3 1 0.84 −2.31 3.76 −3.15 2.92 3 0.65−1.14 2.42 −1.79 1.77 5 0.54 −0.81 1.94 −1.36 1.39

Next, the following show the simulation results of CSI-RS based deltaRSRP for AGWN, ETA5, and ETU 30 when the measurement bandwidth comprises50 RBs.

FIGS. 22a to 22c illustrate CSI-RS based delta RSRP at AGWN, ETA5, andETU30 respectively when the measurement bandwidth comprises 50 RBs.

Each figure shows a CDF as the reference SNR varies from −10 dB to −8,−6, −3, and 0 dB.

As shown in FIGS. 22a to 22c , Table 16 summarizes the simulation resultof CSI-RS based delta RSRP for AGWN, ETA5, and ETU30 when themeasurement bandwidth comprises 50 RBs.

TABLE 16 Measurement Propagation SNR interval 2RE condition [dB] (i*160ms), i 50% 5% 95% [5-50%, 95-50%] AWGN −4 1 0.91 −0.94 2.44 −1.85 1.53 30.63 −0.40 1.62 −1.04 0.99 5 0.55 −0.25 1.35 −0.81 0.80 −3 1 0.74 −0.862.07 −1.60 1.33 3 0.50 −0.37 1.36 −0.87 0.85 5 0.42 −0.24 1.11 −0.660.69 0 1 0.45 −0.56 1.37 −1.01 0.92 3 0.30 −0.30 0.87 −0.59 0.57 5 0.25−0.21 0.71 −0.46 0.46 3 1 0.27 −0.38 0.91 −0.65 0.63 3 0.18 −0.21 0.56−0.39 0.38 5 0.14 −0.16 0.45 −0.30 0.31 EPA5 −4 1 1.11 −3.20 5.09 −4.323.98 3 0.97 −1.35 3.60 −2.32 2.62 5 0.93 −0.97 3.00 −1.90 2.07 −3 1 1.04−3.28 5.04 −4.32 4.00 3 0.94 −1.46 3.55 −2.39 2.61 5 0.86 −1.03 2.93−1.89 2.07 0 1 0.85 −3.61 4.93 −4.47 4.07 3 0.73 −1.64 3.44 −2.37 2.70 50.68 −1.16 2.80 −1.84 2.12 3 1 0.78 −3.62 4.88 −4.40 4.09 3 0.69 −1.793.39 −2.47 2.70 5 0.61 −1.29 2.78 −1.90 2.17 ETU30 −4 1 1.14 −1.82 3.59−2.96 2.45 3 0.89 −0.81 2.37 −1.69 1.48 5 0.77 −0.54 1.95 −1.31 1.18 −31 0.98 −1.92 3.47 −2.89 2.49 3 0.76 −0.90 2.23 −1.66 1.47 5 0.66 −0.591.80 −1.26 1.13 0 1 0.81 −1.80 3.24 −2.61 2.43 3 0.60 −0.86 2.01 −1.461.41 5 0.52 −0.61 1.62 −1.13 1.10 3 1 0.75 −1.80 3.16 −2.55 2.41 3 0.54−0.90 1.94 −1.44 1.40 5 0.47 −0.65 1.56 −1.11 1.10

Considering RF defect of about 3 dB for absolute RSRP and 1 dB forrelative RSRP, the present document proposes absolute and relativeaccuracy required for RSRP measurement for each SNR condition from thesimulation results above. And based on the proposed absolute andrelative accuracy, the minimum required measurement interval (160 ms*itimes) is proposed as shown below.

TABLE 17 Measurement interval (i*160 ms), i Measurement bandwidth 6RB25RB 50RB SNR −4 −3 0 3 −4 −3 0 3 −4 −3 0 3 dB dB dB dB dB dB dB dB dBdB dB dB Proposed absolute 8 8 7 7 7 7 6 6 6 6 6 6 accuracy of RSRP (dB)Proposed relative 6 6 6 6 6 6 6 6 6 6 6 6 accuracy of RSRP (dB) AWGN 3 11 1 1 1 1 1 1 1 1 1 EPA5 5 3 5 5 3 3 5 5 5 5 5 5 ETU30 5 3 5 3 3 3 3 3 33 3 3 Max (AWGN, EPA5, 5 3 5 5 3 3 5 5 5 5 5 5 ETU30)

I-3. Summary of Simulation Results

Form the experimental results above, propositions may be summarized asfollows.

Proposition 1: in case the measurement bandwidth according to the firstdisclosure of the present invention comprises 6, 25, and 50 RBs, Table13 shows the minimum required measurement interval (160 ms*i times) forsatisfying measurement accuracy of CRS-based RSRP.

Proposition 2: the first disclosure of the present invention proposesCSI-RS based RSRP measurement accuracy as the absolute RSRP measurementaccuracy, and in case the measurement bandwidth comprises 6, 25, and 50RBs, Table 17 shows the minimum required measurement interval (160 ms*itimes) for satisfying CSI-RS based RSRP absolute measurement accuracy.

II. The Second Disclosure of the Present Invention

The second disclosure of the present invention proposes acquisition ofPSS/SSS out of a discovery signal, simulation result of acquiringtransmission point (TP), and simulation result of cell/TP identification(including cell detection and cell measurement) through PSS/SSS out ofthe discovery signal.

II-1. Simulation Environment

II-1-1. Simulation Environment for Acquisition of PSS/SSS Out ofDiscovery Signal

Table 18 shows the parameters of a simulation environment for acquiringPSS/SSS out of the discovery signal and cell identification.

TABLE 18 Parameter Unit Cell 1 Cell 2 Cell 3 E-UTRA RF channel number —Channel 1 Channel 1 Channel 1 PSD (Power Spectrum Density) of dB 0 0 0data and control channel with respect to the PSD of reference signal(RS) PSD of PSS and SSS with respect dB 0 0 0 to PSD of RS Carrierfrequency GHz 3.5 3.5 3.5 Number of RBs 6 6 6 RB utilization rate % 100100 100 Data modulation method — QPSK QPSK QPSK Frame structure type —FDD FDD FDD CP length — Normal Normal Normal Frequency offset withrespect to Hz 0 0 0 the UE frequency reference Relative delay via firstpath μs 0 0 CP/2 (synchronous) Es/Noc dB 5.18 0.29 Test 1: 1.25 Test 2:0.25 Test 3: −0.75 Number of transmitting antennas — 1 1 1 PSS sequenceID — See Table 20 See Table 20 See Table 3, 4 and 21 and 21 SSS sequenceID — See Table 20 See Table 20 See Table 3, 4 and 21 and 21 Propagationcondition — AWGN, EPA5, ETU30 Noc model — AWGN PSS/SSS period ms 40 ms,80 ms, 160 ms

Table 19 shows other parameters for simulation of cell identification.

TABLE 19 Simulation parameter Description UE is aware of cell 1 and 2 inadvance Yes Carrier frequency of cell 1, 2, and 3 The same Threshold fordetection failure Required as in an actual UE Indication as to whetherthe UE No is aware of the information about whether a system correspondsto a synchronous or asynchronous system Duty cycle 100% (to representnon-DRX case) Performance reference for comparison Acquisition time toachieve 90% of accurate cell detection for a sequence ID of PSS and SSSCP length detection Both short and long CP (namely extended CP) exist,and the UE has to detect CP length. The number of receiving antennas 2(uncorrelated)

Table 20 shows combinations of cell IDs.

TABLE 20 Cell 3 Cell 1 Cell 2 Case (Target cell) (Interference source 1)(Interference source 2) Scenario 1 psc3 ssc3a, ssc3b psc1 ssc1a, ssc1bpsc2 ssc2a, ssc2b Synchronization 2 psc1 ssc3a, ssc3b psc1 ssc1a, ssc1bpsc2 ssc2a, ssc2b Synchronization 3 psc1 ssc1a, ssc3b psc1 ssc1a, ssc1bpsc2 ssc2a, ssc2b Synchronization 4 psc3 ssc1a, ssc1b psc1 ssc1a, ssc1bpsc2 ssc2a, ssc2b S Synchronization

Meanwhile, PSC and SSC index for simulation are summarized as follows.

TABLE 21 Level Code index psc1 29 psc2 25 psc3 34

TABLE 22 Level Code index Cell group index (ssc1a, ssc1b) (6, 8) 36(ssc2a, ssc2b) (10, 12) 40 (ssc3a, ssc3b) (7, 9) 37 (ssc1a, ssc3b) (6,9) 65

II-1-2. Simulation Environment for Acquisition of CSI-RS Out ofDiscovery Signal

It is assumed that the UE is aware of all of information (subframe, REconfiguration, and scrambling initialization information) about CSI-RStransmitted from three TPs.

Table 23 shows simulation parameters for acquiring a CSI-RS.

TABLE 23 Parameter Unit TP1 TP2 TP3 (Desired TP) E-UTRA RF channelnumber — Channel 1 Channel 1 Channel 1 PSD of data and control channeldB 0 0 0 with respect to the PSD of RS PSD of PSS and SSS with respectdB 0 0 0 to the PSD of RS Carrier frequency GHz 3.5 3.5 3.5 Number ofRBs 6 RB, 50 RB RB utilization ratio % 100 100 100 Data modulationmethod — QPSK QPSK QPSK Frame structure type — FDD FDD FDD CP length —Normal Normal Normal Frequency offset with respect to Hz 0 0 0 UEfrequency reference Relative delay via first path (synchronous) μs 0 0CP/2 Es/Noc dB 10 5 Test 1: −2 dB Test 2: 0 dB N^(cell) _(ID) (N^(CSI)_(ID) is the same as N^(cell) _(ID)) 3 3 3 The number of transmitting —1 1 1 antennas Antenna port — 15 15 15 CSI-RS configuration index — 10 50 CSI- — 40/3, 80/3, 160/3 RS period and subframe offset (T_(CSI-RS)/I_(CSI-RS)) Muting for CSI-RS Yes Propagation condition — AWGN, EPA5,ETU30 Noc model — AWGN CSI-RS period — 40 ms, 80 ms, 160 ms

Table 24 shows other parameters for simulation of cell identification.

TABLE 24 Simulation parameter Description UE is aware of TP 1 and 2 inadvance Yes Carrier frequency of TP 1, 2, and 3 The same Threshold fordetection failure Required as in an actual UE Duty cycle 100% (non-DRXcase) Performance reference for comparison Acquisition time to achieve90% of accurate TP ID of the CSI-RS CP length detection Both short andlong CP (namely extended CP) exist, and the UE has to detect CP length.The number of receiving antennas 2 (uncorrelated) Failure alarm rate 1%

Also, performance metrics are as follows.

1) Acquisition of PSS/SSS

-   -   Criterion for successful event: acquisition of accurate PSS/SSS    -   Required success rate: 90%    -   Expected result from simulation: delay in acquiring PSS/SSS

2) Acquisition of CSI-RS

-   -   Criterion for successful event: acquisition of accurate CSI-RS    -   Required success rate: 90%    -   Expected result from simulation: delay in acquiring CSI-RS

II-2. Simulation Result

II-2-1. Simulation Result for Acquiring PSS/SSS

FIGS. 23a to 23c illustrate Pd with respect to acquisition time(AcqTime) when Es/Noc=−0.75 dB, and propagation condition corresponds toAGWN, EPA5, and ETU30 respectively.

FIGS. 23a to 23c show Pd with respect to acquition time (AcqTime) whenthe DMTC measurement period changes to 40, 80, and 160 ms, respectively.

Meanwhile, Table 25 shows PSS/SSS acquisition time (x: times of DRSperiodicity) to achieve 90% success rate when the DMTC measurementperiod changes to 40, 80, and 160 ms.

TABLE 25 AWGN EPA5 ETU30 Es/Noc(dB) DRS_Periodicity*x −0.75 0.25 1.25−0.75 0.25 1.25 −0.75 0.25 1.25 Case1 40 ms 7 4 2 13 8 6 14   8 6 80 ms8 4 2 10 7 4 14   9 6 160 ms  7 4 2 9 6 4 15   9 6 Case2 40 ms 14 4 2 169 6 19 10 7 80 ms 13 4 2 12 7 5 21 10 6 160 ms  14 4 2 11 6 4 15 10 6Case3 40 ms 12 4 2 18 9 7 20 10 6 80 ms 11 4 2 12 7 5 21 10 6 160 ms  114 2 11 7 5 15 10 6 Case4 40 ms 6 3 2 13 8 6 13   9 6 80 ms 6 3 2 10 6 414   8 6 160 ms  6 4 2 9 6 4 15   8 6

Table 25 above indicates the values not satisfying the criterion byunderlining them.

From the results shown in Table 25, Table 26 shows the number of DSperiods for each case.

TABLE 26 Max (AWGN, DRS_Periodicity * x EPA5, ETU30) Es/Noc(dB) −0.750.25 1.25 Case1 40 ms 14 8 6 80 ms 14 9 6 160 ms  15 9 6 Case2 40 ms 1910 7 80 ms 21 10 6 160 ms  15 10 6 Case3 40 ms 20 10 7 80 ms 21 10 6 160ms  15 10 6 Case4 40 ms 13 9 6 80 ms 14 8 6 160 ms  15 8 6 Max(case1, 40ms 20 10 7 case2, 80 ms 21 10 6 case3, 160 ms  15 10 6 case4)

II-2-2. Simulation Result for Acquiring CSI-RS

Table 27 shows CSI-RS acquisition time (x: times of DRS periodicity) toachieve 90% success rate when the DMTC measurement period changes to 40,80, and 160 ms.

TABLE 27 AWGN EPA5 ETU30 Es/Noc(dB) DRS_Periodicity*x −2 0 −2 0 −2 0 6RB 40 ms 15  5 14  7 9 5 80 ms 16  5 11  6 9 5 160 ms  17  5 9 5 10 515RB 40 ms 4 1 7 4 5 2 80 ms 4 1 5 3 5 2 160 ms  5 1 5 3 5 2 25RB 40 ms2 1 4 2 3 2 80 ms 2 1 3 2 3 2 160 ms  2 1 3 2 3 2 50RB 40 ms 1 1 2 1 1 180 ms 1 1 2 1 1 1 160 ms  1 1 2 1 1 1

Table 27 above indicates the values not satisfying the criterion byunderlining them.

From the results shown in Table 27, Table 28 shows the number of DSperiods for each case.

TABLE 28 Max (AWGN, DRS_Periodicity * x EPA5, ETU30) Es/Noc (dB) −2 0  6RB 40 ms 15 7 80 ms 16 6 160 ms  17 5 15 RB 40 ms 7 4 80 ms 5 3 160 ms 5 3 25 RB 40 ms 4 2 80 ms 3 2 160 ms  3 2 50 RB 40 ms 2 1 80 ms 2 1 160ms  2 1

II-3. Summary of Simulation Results

Form the simulation results above, propositions may be summarized asfollows.

Proposition 1: the number of periods for a discovery signal with respectto acquisition of PSS/SSS is shown in Table 26.

Proposition 2: the number of periods for a discovery signal with respectto acquisition of CSI-RS is shown in Table 28.

The embodiments of the present invention described above may beimplemented by using various means. For example, the embodimentsaccording to the present invention may be realized through hardware,firmware, software, or a combination thereof. More specifically, theimplementation will be described with reference to appended drawings.

FIG. 24 illustrates a block diagram of a wireless communication systemin which the present invention is implemented.

An eNB 200 includes a processor 201, memory 202, and RF (RadioFrequency) unit 203. The memory 202, being connected to the processor201, stores various kinds of information for operating the processor201. The RF unit 203, being connected to the processor 201, transmitsand/or receives a radio signal. The processor 201 implements a proposedfunction, process and/or method. In the embodiments described above,operation of the eNB may be realized by the processor 201.

A UE 100 includes a processor 101, memory 102, and RF (Radio Frequency)unit 103. The memory 102, being connected to the processor 101, storesvarious kinds of information for operating the processor 101. The RFunit 103, being connected to the processor 101, transmits and/orreceives a radio signal. The processor 101 implements a proposedfunction, process and/or method.

The processor may comprise Application-Specific Integrated Circuit(ASIC), other chipsets, logical circuit, and/or data processing device.The memory may include Read-Only Memory (ROM), Random Access Memory(RAM), flash memory, memory card, storage medium and/or other storagedevices. The RF unit may include a baseband circuit for processing aradio signal. If an embodiment is implemented by software, thetechniques described above may be implemented in the form of a module(process or function) which performs the function described above. Amodule may be stored in the memory and may be executed by the processor.The memory may be located inside or outside the processor and may beconnected to the processor through a well-known means.

The embodiments of the present invention above are described by usingflow diagrams comprising steps or blocks, but the present invention isnot limited to the specific order of steps; some steps may be performedin a different order with other steps or may be performed simultaneouslywith other steps. Also it should be understood by those skilled in theart that the steps introduced in the diagrams are not exclusive to eachother, other steps may be added, or one or more steps may be deletedwithout affecting the technical scope of the present invention.

What is claimed is:
 1. A method for performing measurements based on adiscovery signal, the method comprising: receiving, from a cell, acell-specific reference signal (CRS) based discovery signal; andperforming measurements based on the CRS based discovery signal during apredetermined measurement period; wherein if a measurement bandwidthcorresponds to 6 resource blocks (RBs), the predetermined measurementperiod is determined to be equal to 5*an occasion periodicity formeasuring the discovery signal, wherein if the measurement bandwidthcorresponds to 6 RBs, the predetermined measurement period is determinedto be equal to 3*the occasion periodicity for measuring the discoverysignal, and wherein the discovery signal is received during an occasionduration defined as N consecutive subframes.
 2. The method of claim 1,wherein the occasion periodicity for measuring the discovery signalcorresponds to one of 40 ms, 80 ms, and 160 ms.
 3. The method of claim1, wherein a value of the N is equal to or more than one.
 4. The methodof claim 1, wherein in the performing of the measurement, adiscontinuous reception (DRX) is not used.
 5. The method of claim 1,wherein the discovery signal includes one or more of a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),a cell-specific reference Signal (CRS) and a channel state informationreference signal (CSI-RS).
 6. A terminal for performing measurementsbased on a discovery signal, the terminal comprising: a radio frequency(RF) unit configured to receive, from a cell, a cell-specific referencesignal (CRS) based discovery signal; and a processor configured toperform measurements based on the CRS based discovery signal during apredetermined measurement period, wherein if a measurement bandwidthcorresponds to 6 resource blocks (RBs), the predetermined measurementperiod is determined to be equal to 5*an occasion periodicity formeasuring the discovery signal, wherein if the measurement bandwidthcorresponds to 6 RBs, the predetermined measurement period is determinedto be equal to 3*the occasion periodicity for measuring the discoverysignal, and wherein the discovery signal is received during an occasionduration defined as N consecutive subframes.
 7. The terminal of claim 6,wherein the occasion periodicity for measuring the discovery signalcorresponds to one of 40 ms, 80 ms, and 160 ms.
 8. The terminal of claim6, wherein a value of the N is equal to or more than one.
 9. Theterminal of claim 6, wherein in the performing of the measurement, adiscontinuous reception (DRX) is not used.
 10. The terminal of claim 6,wherein the discovery signal includes one or more of a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),a cell-specific reference Signal (CRS) and a channel state informationreference signal (CSI-RS).